It's no lie to say Warfronts were not worth the hype blizz set up in BfA, but if Blizz were to decide to redeem it with some well needed changes to how it works so that their more fun what themes would you like to see
Dwarves vs Tauren, or Gnomes vs Trolls go without saying since it would round out themes for the original 8 races, but we could go farther
Personally, I kind of like the idea of Worgen vs Mag'har, with both being more industrialized counterparts to the main races, with Worgen mail giving a musketeer sort of appearance while Plate gets a dark knight flavor compared to Stormwind(with an open mouth helmet to fit Worgen better), and Mag'har plate being a mix of the Blackrock set from WoD and the Mag'har heritage armor while Leather gets a set based on the Shattered hand Orc models and mail being based on the Frostwolves